1. This invention is in the field of Stirling Cycle refrigerators or coolers.
2. There are various applications which require coolers capable of cooling to 10.degree. K. Stirling Cycle coolers for such a temperature usually employ at least two stages of cooling with a regenerator at each stage. Typical of such coolers is U.S. Pat. No. 4,143,520 of Mar. 13, 1979, to Zimmerman. This patent shows a four-stage cooler with a nylon displacer and an epoxy-glass composite cylinder closely surrounding the displacer, but does not show nor describe any discrete regenerator. Lines 61 and 62 of column 2, however, describe how cryogenic fluid picks up heat from the walls of the annular gap in a displacer-cylinder combination. This is a very low efficiency regenerator, a great disadvantage. For best operation of his invention, Zimmerman adjusts the displacer with respect to the cylinder: "After initial cool-down" (column 6, lines 34 and 35). This is another of the disadvantages of the Zimmerman invention. Yet another is that the cylinder, being made of an epoxy-glass composite, is porous to helium and the helium will leak into the vacuum between the cylinder and the metal housing surrounding the cylinder. The instant invention, because of its construction, does not have these disadvantages.